Is it time for a new mattress? Do you wake up tired or achy, or does your mattress look saggy or lumpy? Or maybe you sleep better at hotels?

Consumer Reports offers these mattress-buying tips:

Lie down. If possible, lie on any mattress you’re considering. Wear loose clothes and shoes you can slip off. Make yourself comfortable, and shoo away the sales representative if you’re feeling pressured. Spend at least five or 10 minutes on each side and on your back (your stomach, too, if that’s a preferred sleeping position). Shopping online or at a warehouse club? Tryouts aren’t usually an option, so checking return policies before you buy is extra important.

Inspect return periods. Make sure the store offers a full refund or credit toward another mattress. Return periods, often called “comfort guarantees,’’ range from a couple of weeks to 120 days. Some retailers, including Macy’s and Sears, charge a 15 percent restocking fee. Costco and some online sellers provide free pickup if you want a refund or exchange, but otherwise, you’ll have to pay for it — or cart the mattress to the store. You’ll be responsible for any damage.

Try to haggle. Once you’ve settled on a model, try to bring the price down. Many businesses, such as warehouse clubs, have fixed prices and won’t budge. But for retailers that do negotiate — particularly specialty chains — huge markups allow them to lower prices by 50 percent or more during their frequent sales. One recommendation: Any time of year, insist on a sale price you’ve seen for the mattress you know you want, and don’t be afraid to walk out if you feel you’re getting a raw deal.

Don’t be bullied into a box spring. You might not need it. For an innerspring mattress, the box spring (also called a “foundation’’) is a wood frame enclosing stiff wire and covered with fabric to match the mattress. For foam or adjustable air mattresses, it’s a box several inches high. If you’re switching to a foam or adjustable air bed from an innerspring, you’ll need a boxy foundation that lacks springs and wire. Otherwise, if your box spring isn’t broken and is still structurally sound, consider keeping it and saving money (about $150 to $300 for a queen size). One caveat: Some brands require you to buy their box spring to receive full warranty coverage.

Understand the warranty. It can range from 10 to 25 years and covers only manufacturing defects such as sagging and loose or broken coil wires. Coverage is frequently prorated, meaning that it decreases over time.

Delivery day. Never accept delivery without inspecting the mattress (and box spring) for stains and other damage. Be sure that the mattress has a label that states “all-new material’’ before you send the driver on his way. If it’s not there, refuse delivery.